1. Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor light-emitting device, and more particularly to a production method whose characteristic feature resides in a process for forming an MQW layer.
2. Background Art
As has been hitherto known, a Group III nitride semiconductor light-emitting device includes a light-emitting layer having an MQW structure in which InGaN well layers and AlGaN barrier layers are alternately stacked in a repeated manner.
Patent Document 1 discloses a Group III nitride semiconductor light-emitting device including an MQW-structure layer in which well layers and barrier layers are alternately stacked in a repeated manner, wherein the barrier layers are formed from AlxGa1-xN having an Al compositional ratio x of 3 mol % to 6 mol %. This patent document also describes that the device has an emission wavelength of 460 nm to 470 nm. However, the patent document does not refer to the relationship between the Al compositional ratio of the barrier layers and the emission wavelength of the device.
Patent Document 2 discloses a semiconductor light-emitting device including an MQW-structure layer in which well layers and barrier layers are alternately stacked in a repeated manner, wherein the well layers are formed from InyGa1-yN having an In compositional ratio y of 5 mol %, and the barrier layers are formed from AlxGa1-xN having an Al compositional ratio x of 13 mol %. This patent document describes that the Al compositional ratio x of the barrier layers is desirably 6 mol % to 18 mol %, but does not particularly describe the emission wavelength of the device.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2006-332365    Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2000-91629
However, in the case where a barrier layer of an MQW-structure layer is formed from AlxGa1-xN, when the Al compositional ratio x of the barrier layer is high, carrier injection performance is lowered, whereas when the Al compositional ratio x of the barrier layer is low, carrier confinement performance is lowered, which results in low output of a light-emitting device. Therefore, in order to improve the output of the light-emitting device without impairing the function of the barrier layer, the Al compositional ratio x of the barrier layer must be determined according to the emission wavelength of the device. In each of the light-emitting devices disclosed in Patent Documents 1 and 2, the Al compositional ratio x of the barrier layer is not optimized in association with the emission wavelength of the device.